Electrical heating device



NOV- 22, 1966 A. ARMBRUSTER, JR 3,287,684

ELECTRICAL HEATING DEVICE Filed Feb. 27. 1964 2 Sheets-Sheet 1 ATTORNEY ALBERT ARMBRUSTER JR.

Byamgm/ Nov. 22, 1966 A. ARMBRUSTER, JR 3,287,684

ELECTRICAL HEATING DEVI GE Filed Feb. 27, 1964 2 Sheets-Sheet 2 INV ENTOR. ALBERT ARMBRUSTER JR,

ATTORNEY United States Patent O 3,287,684 ELECTRICAL HEATING DEVICE Albert Armbruster, Jr., Glenside, Pa., assignor to Motson Services Incorporated, a corporation of Pennsylvania Filed Feb. 27, 1964, Ser. No. 347,866 5 Claims. (Cl. SSS- 211) This invention relates to heating -devices and more particularly to electrical heating devices.

Electrical heating devices as known to the prior art have been fabricated by providing a relatively high resistance wire to be held in the device which -applies the heat and by providing some means for connecting an electrical power input thereto. For' instance in an electric blanket, a plurality of relatively high resistance wires are connected in series or in a parallel-series arrangement, and are located within the double layer of the blanket. When an electrical power is applied to the resistance wires, the wires oppose the current flow and the energy used to maintain the current flow is given off in the f-orm of heat. Many other devices employ in general the same principle of a series connected high resistance wire with a power source to Igenerate heat, such as a therapeutic heating pad, automobile Vseat warmers, .hot food warmers, and the like.

yFlurther, electrical heaters -as known to the prior art have been confined to a predetermined shape and size. That is to say that once a prior art electrical heater is made an alteration (size or shape) thereof would be difticult if not impossible.

The present invention provides an electrical heating device which can be built on either a flexible (benda-ble) base or on a stili base to accommodate either wrap around utility or stationary utility. In addition, the present heating device can be cut to any shape or size without impairing t-he operation of the remaining portion of the heating device.

Accordingly it is an'object of the present invention to provide an improved electrical heating device.

It is a further object of the present invention to provide an electrical heating device which can be cut into any shape or size by cutting away a portion without impairing the operation of the remaining portion of the heating device.

It is a further object of the present invention to provide an electrical heating device which can generate heat with an equal distribution over its entire surface.

In accordance with a feature of the present invention, electrical resistance mate-rial is placed on a substrate (or substrate is resistive in itself) which can be cut and shaped. On or below to the electrical resistance material there is place-d a plurality of distribution bus bars with header bus bars supplying electrical current thereto. The electrical current is transmitted from one distribution bus bar to an adjacent `distribution bus bar through the electrica-l resistance material to generate heat. v

In accordance with another feature of the present invention 'the distribution bus bars are located on the resistance material with respect .to theheader bus bars in such a way that they can be cut away at positions lying away from the header bus bars input terminals so as to allow electrical current to flow through the resistance material between the remaining distribution bus bars, thereby generating heat in the resistance material remaining after the portion has been cut away.

In accordance with another feature of the present in-` vention the substrate can be made `of a flexible material to permit a wrap around application.

In accordance with another feature of the present invention there are provided varying wdith bus bars which are further made so as to possess a characteristic of significant 3,287,634 Patented Nov. 22, 1966 resistance, which provide equal current distribution therealong to be transmitted through the resistance material in order to produce a uniform heat ygeneration over the entire surface of the device including the bus bars.`

In accordance with another feature of the present invention, the distribution bus bars are located parallel to the header bus bars to receive and distribute electrical current even though a portion of the heater may be removed from the central portion of the device.

The foregoing `and other objects and -features of the invention will be best understood by reference to the following description of certain embodiments of the invention taken in conjunction with the accompanying drawings wherein:

FIGURE l is a schematic view of the present invention with the header bus bars located along the same edge `of the layer of resistance material;

FIGURE 2 is an end view of FIGURE 1 along line 2 2;

IIGURE 3 is a detailed view of `a crossover point in FIGURE 1;

FIGURE 4 is a schematic view of an embodiment of the present invention with the heade-r bus bars on opposite sides of the resistance material;

FIGURE 5 is a schematic view of an embodiment showing the varying width bus bars;

FIGURE 6` is a schematic view of an embodiment showing the distribution bus bars lying parallel to the header bus bars.

Consider FIGURE l which shows the heating device of the present invention in a preferred embodiment. In FIGURE l there is shown an electrically non-conducting substrate 11. The substrate 11 can be any electrically non-conducting material such as -ceramic or plastic, but preferably a material which can be cut by a scissors, knife or saw. In the preferred embodiment an isocyanate impregnated glass cloth is used. Some of the products which have been successfully employed as substrates are known yby their trade names, (Stiff) Isoglass, manufactured by the Natwar Corporation and Tedlar, Teflon and Pyre-M.L., manufactured by Du Pont.

On the upper surface of the substr-ate 11 there is secured a layer of electrical resistance material 13. The electrical resistance material can be any resistance material held in a binder which can be applied by a printing techniqrue. For instance in the preferred embodiment the resistance material is a mixture of polyester resin, graphite and a solvent. The ratio of graphite to resin varies depending on the value of the resistance factor to be used in the heater. The resistance material 13 is applied to the sub-l strate 11 by means of a silk screen printing technique, however spraying and other forms of thin film applications can be employed.

O-n to the upper portion of the substrate two header bus bars 15 and 17 are printed. The header bus bars are made of conducting ink which in thepreferred embodiment is a polyester resin mixed with silver akes and a solvent. An example of such an acceptable ink is Silver No. SSOLA, manufactured Iby Dupont. The header =bus bars 15 and 17 are printed with a silk screen printing technique, although as mentioned earlier with respect to the resistance material, other forms of thin lrn applications can be employed.

`Connected to the header bus rbars 15 and 17 are seven distribution bus Ibars 19 through 25. The distribution bus bars 19 through 25 are made of conducting ink and as mentioned in connection with the header bus bars, in the preferred embodiment are fabricated from a polyester resin, silver flakes and a solvent.

The distribution bus b-ars 20, 22 and 24 are connected to the header bus bar 17. The distribution bus Ibars 20, 22 and 24 are printed on the electrical resist-ance material 3 6 13 with a silk screen printing technique, although other thin -lm application techniques are pos-sible.

The `distribution bus bars 19, 21, 23 and 25 are connected to the header bus bar 15. These last mentioned distribution bus bars are also printed with a silk screen printing technique although other methods may be employed. However before the distribution bus bars 21, 23 and 25 are printed a small area of header bus bar 17 is covered with insulation material. The insulation bridges 27, 29 and 31 can lbe layers of epoxy resin, bondable Mylar and the like.

The insulation bridges 27, 29 and 31 electrically isolate the distribution bus bars 21, 23 and 25 from the header 4bus bar 17, thereby providing for electrically isolated circuit terminals between bus bar 21 and bus bars 20 .and 22; bus bar 23 with b-us bars 22 and 24; and nally between bus bars 24 and 25. There is also a circuit path between bus bars 19 and 20= but this does not necessitate an insulation bridge since bus bar 19 does not cross over header bus -bar 17.

Connected to the header bus bars 15,-and 17 are two electrical power terminals. The power applied can be either A.C. lor D.C. power. In an A.C. power Inode, the voltages can run between 15 volts and 260` volts, while a low D.C. voltage on the order of l2 to 28 volts should be applied when operating in the D.C. mode.

Consider that header bus bar 15 is subjected to a positive potential while header bus bar 17 is subjected to a negative potential. Electrical current would flow along header bus bar 15, down each of the distribution bus bars 19, 21, 23 and 25 through the resistance material 13 which lies between the distribution bus bars to distribution bus bars 24 (from bars 23 and 25), 22 (-from bars 23 and 21), `and 20 (from bars 21 yand 19). As the current passes through the layer of resistance material 13, heat is generated uniformly over the entire surface. 1f the device is without a heat sink it has been found preferable to tix the parameters to produce 50` Watts/sq. ft., While if a heat sink is used (for instance mounting the device on metal), it has been found that the device can be operated satisfactorily to produce 430 watts/sq. ft.

FIGURE 2 shows an end view of the device of FIG- URE 1 taken along the line 2 2 with the identification numerals being identical to those in FIGURE l.

FIGURE 3 is a detailed view of a small area around the insulation bridge 27 of FIGURE 1. The identifcation numerals are identical to those in FIGURE l and the ligure is clearly self explanatory when considered with the foregoing description.

The embodiment of FIGURES 1, 2 and 3 has the advantage that three sides or edges of the device lie away from the header bus bar terminals so that the heater device can be cut on these three sides. For instance if it were desirable to provide a heating device with the peculiar shape designated by line 35, the heating device of FIGURE 1 could 4be cut along line 35 and that portion which lies toward the header bus bar terminals would produce heat, while the cut-away portion 39 would not produce heat.

The foregoing rfeature enables the heater device of the present invention to be mass produced and simply tailored to suit the needs of the user as required at the time of nsmg.

In the description of FIGURES 4, 5 and 6, it will be understood that the non-conducting substrates, the resistance material, the header lbus bars and the distribution bus bars will all be fabricated of the same material and printed with the same techniques as described above in connection with the device ofFIGURE 1. Therefore, the description to follow will not include references to the materials and techniques unless there is a difference from the device of FIGURE 1.

In FIGURE 4 it will be noted that the header bus bars 41 and 43 lie on opposite edges of lche layer of resistance material 13. The distribution bus bars 45, 47 and 49 are connected to header bus 41 while the distribution bus bars 51, 53 and 55 are connected to the header bus bar 43. For current flow study, consider the header bus bar 43 as having a positive voltage applied thereto and header bus bar 41 as having a negative voltage 4applied thereto. Conventional current will flow from header bus bar 43 along the distribution b-us bars 51, 53 and 55- through the resistance material 13 to the distribution bus bars 45, 47 and 49 thereby generating heat in the resistance material 13 as described above. The heater device of FIG- URE 4 can be cut along the line 54 and the portion to the left will generate heat in response to electrical power being applied to its input terminals, while the portion to the right will not generate heat.

FIGURE 5 shows an embodiment of the present invent-ion which enables the bus bars to be rnade resistive and therefore heat producing. Graphite is added to the polyester resin b-inder of the conductive ink to render the ink resistive in nature. The bus bars are all tapered `as shown so that the current distribution is equal along the length of the bus bars. For instance, the wide part of the bus bar enables more current to be carried with the same rated wattage dissipation as the narrow end of the bus bar. Hence, the entire surface generates heat, i.e., the bus bars las well as the resistance material between the bus bars.

FIGURE 6 shows an embodiment to accommodate holes in the heating device. If a hole for instance were formed in the central portion of the embodiment of FIGURE 1 which out through a distribution bus bar, the area Ibelow the hole would be cole (i.e., no heat would 4bep-roduced), since there would be no complete return path for the current. In FIGURE 6 current passes from header bus lbar 59 to header bus bar 611 (assuming of course the proper voltages).

As the current passes from header bus bar 59 to header bus bar 61 the d-istribution bus bars serve to intercept and distribute the current. If there are no breaks or holes in t-he device, t'he distribution bus bars merely act as small short circuited areas. When there is a hole in the central area (for instance possibly to accommodate -a iluid carrying pipe) the current arriving at distribution Ibus bar 63 will vbe distributed therealon-g to pass on to the halves 64 and 65 of the yadjacent distribution bus bar. This pattern follows throughout.

The present invention provides a flexible and easily produced electrical heating device. It can be shaped and cut to accommodate the needs of the user without great effort and the heat distribution is uniform over the entire heating surface.

While I have described -above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example an-d not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. An integral electrical heating device comprising: an electrically non-conducting `substrate of readily cuttable material; a layer of electrical resistance material secured to said nonconducting substrate; at least first and second header bus -bars secured to said non-conducting substrate, said first and second header bus bars lying along the same edge of said layer of electrical resistance material and being `adapted to be connected to a power supply; a plurality of distribution bus bars of printable electrically conducting Imaterial disposed substantially parallel to each other and in contact with and along said layer of electrical resistance material; said header bus bars and said distribution bus bar being fabricated of printable electrically conducting material; a rst ygroup of said plurality of distribution bus bars connected to said first header bus bar and a second group of said plurality of distribution 'bfus bars connected to said second header bUS bar, Said rst group of distribution bus bars trans- 5 miting current through said electrical resist-ance material to said second group of distribution bus bars to generate heat as said current passes through said electrical resistance material.

2. An electrical heating device accord-ing to claim 1 wherein said first distribution bus bars cross over said second header bus bar and Whereat each of said rst distribution bus bars crosses over said second header bus bar there -is further disposed printable insudation means to electrically isolate said rst distribution Ibus bars from said second he-ader bus bar.

3. An electrical heating device according to olaim 1 wherein sa-id non-conducting substrate is a flexible substrate.

4. An electrical heating device according to claim 1 wherein said layer of resistance material includes grapfhite held in a polyester resin.

5. An electrical heating device according to claim 1 wherein said distribution bus bars are fabricated of oonducting ink which includes a polyester resin and silver akes.

References Cited by the Examiner UNITED STATES PATENTS RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

1. AN INTEGRAL ELECTRICAL HEATING DEVICE COMPRISING: AN ELECTRICALLY NON-CONDUCTING SUBSTRATE OF READILY CUTTABLE MATERIAL; A LAYER OF ELECTRICAL RESISTANCE MATERIAL SECURED TO SAID ON-CONDUCTINNG SUBSTRATE; AT LEAST FIRST AND SECOND HEADER BUS BARS SECURED TO SAID NON-CONDUCTING SUBSTRATE, SAID FIRST AND SECOND HEADER BUS BARS LYING ALONG THE SAME EDGE OF SAID LAYER OF ELECTRICAL RESISTANCE MATERIAL AND BEING ADAPTED TO BE CONNECTED TO A POWER SUPPLY; A PLURALITY OF DISTRIBUTION BUS BARS OF PRINTABLE ELECTRICALLY CONDUCTING MATERIAL DISPOSED SUBSTANTIALLY PARALLEL TO EACH OTHER AND IN CONTACT WITH AND ALONG SAID LAYER OF ELECTRICAL RESISTANCE MATERIAL; SAID HEADER BUS BARS AND SAID DISTRIBUTION BUS BAR BEING FABRICATED OF PRINTABLE ELECTRICALLY CONDUCTING MATERIAL; A FIRST GROUP OF SAID PLURALITY OF DISTRIBUTION BUS BARS CONNECTED TO SAID FIRST HEADER BUS BAR AND A SECOND GROUP OF SAID PLURALITY OF DISTRIBUTION BUS BARS CONNECTED TO SAID SECOND HEADER BUS BAR, SAID FIRST GROUP OF DISTRIBUTION BUS BARS TRANSMITTING CURRENT THROUGH SAID ELECTRICAL RESISTANCE MATERIAL TO SAID SECOND GROUP OF DISTRIBUTION BUS BARS TO GENERATE HEAT AS SAID CURRENT PASSES THROUGH SAID ELECTRICAL RESISTANCE MATERIAL. 